1. Technical Field
This invention relates to an alignment apparatus and an alignment method, which are useful, particularly, when used in performing positioning of one workpiece at a predetermined position for the workpiece based on two alignment marks with the use of a plurality of optical means.
2. Related Art
An ink-jet recording apparatus, such as an ink-jet printer or an ink-jet plotter, is equipped with an ink-jet recording head unit (may be hereinafter referred to as a head unit) including an ink-jet recording head which ejects, as ink droplets, ink accommodated in a liquid accommodation portion such as an ink cartridge or an ink tank. The ink-jet recording head has nozzle rows comprising rows of nozzle orifices arranged in parallel, and has its ink ejection surface side covered with a cover head. The cover head has a window frame portion having an opening window portion provided on the ink droplet ejection surface side of the ink-jet recording head for exposing the nozzle orifices, and has a side wall portion formed by being bent from the window frame portion beside the side surface of the ink-jet recording head. The cover head is fixed by having the side wall portion joined to the side surface of the ink-jet recording head (see, for example, JP-A-2002-160376 (page 4, FIG. 3)).
When the cover head and a fixing member, such as a fixing plate, are to be joined to a plurality of the ink-jet recording heads, the ink-jet recording heads are moved with respect to the fixing member for predetermined positioning so that an alignment mark provided in a nozzle plate of the ink-jet recording head aligns with a reference mark provided in a flat plate-shaped glass mask. In more detail, the reference mark and the alignment mark corresponding positionally thereto are simultaneously observed with an optical means having the optical axis pointed in the direction of the alignment mark from the mask side via the reference mark, and the position of the ink-jet recording head is adjusted based on the observation such that the reference mark and the alignment mark are superimposed. Thus, it is desirable for the optical axis of the optical means to be pointed accurately in the direction of the reference mark and the alignment mark.
To achieve the rapidity or rationalization of alignment, in particular, it is conceivable to carry out alignment with two alignment marks of one ink-jet recording head as a workpiece, at a stroke, while observing the two alignment marks by use of optical means such as two microscopes. In this case, it is necessary to make adjustments so as to avoid relative displacement of the optical axes of the respective optical means.
An earlier technology concerned with this type of optical axis alignment was designed to carry out alignment in consideration of the amount of displacement of the alignment mark due to inclination between the optical axis and the alignment mark/workpiece (see, for example, JP-A-2001-153608 (page 4, FIG. 2)).
With the above-mentioned optical axis alignment method according to the earlier technology, however, the amount of displacement needs to be computed, and a correction is made based on the amount of displacement found by computation. Thus, the alignment mark cannot be recognized visually, and alignment based on a human sense is difficult.
Such problems occur not only during alignment associated with the production of an ink-jet recording head unit, but also during alignment associated with the production of other liquid-jet head units.